Characteristics of hydride-like segregates of hydrogen at dislocations in palladium

Abstract

On the basis of multifactor analysis of the most representative experimental data on the solubility, electrical resistance, and diffusivity of hydrogen in palladium specimenswith high and low dislocation densities, it has been shown that the structure, composition, diameter (up to several nm), contribution to electrical resistance, thermodynamic and diffusion characteristics of hydride-like segregates at dislocations inpalladium can vary in wide limits depending on the concentration and thermodynamic activity of hydrogen dissolved in the normal lattice of the metal. The formation of hydride-like segregation phases at dislocations occurs at high degrees ofundersaturation of the solid solutions with respect to the hydride precipitation in the normal lattice of palladium. This means that a specific phase diagram can be considered for a 'hydrogen — near-dislocation segregation Pd nanoregions' system, in comparison with the conventional hydrogen–palladium phase diagram. The results obtained can be used for the description of the apparent concentration and distribution of hydrogen between the normal crystal lattice and defect regions in palladium specimens produced using different processing and treatment methods. In particular, the results can be used for the interpretation of hydrogen influence on the physical and mechanical properties of the materials, and also for revealing themicromechanisms and ways of the optimization of regimes of thermal-hydrogen treatment and governing hydrogen-induced transformation hardening of palladium and palladium-based alloys.